The LOTUS Study: Fluoridation for Adults

How effective and cost-effective is water fluoridation for adults? A 10-year retrospective cohort study.



The LOTUS study is the largest ever study of the effects of water fluoridation on the dental health of adults.

Our study is using real-world anonymised data on 17.8 million adults and adolescents attending NHS dental practices in England to understand the effect of water fluoridation on:

  • the number and types of dental treatments received;
  • the costs of those treatments to the NHS;
  • the costs of those treatments to NHS dental patients.

Only 10% of neighbourhoods in England receive fluoridated water and we can use this variation to look at differences. This is called a ‘natural experiment’.

Part of our work so far has been to map fluoride levels across England to identify who did and who did not receive fluoridated water between 2010 and 2020. We did this using information on fluoride levels in water quality samples provided to us by the water companies.

This information meant that we could estimate a water fluoride level for 99.8% of neighbourhoods (Lower Super Output Areas, LSOAs) in England.

For more information on the anonymised dental data that we hold please refer to the Privacy Notice for our study.

Why fluoridate tap water?

Adding fluoride to the public water supply (fluoridation of tap water) has been strongly promoted by dental professionals since the 1950s. However, only about 10% of the people in England receive water containing close to the government’s recommended fluoride level of 1 mg/litre.

Fewer children now have tooth decay, and more adults keep their permanent teeth into old age. This is put down to using toothpastes that contain fluoride.

In the early 1970s almost everyone experienced decay in their permanent teeth by late childhood and more than a third of adults had no natural teeth. In comparison, today we have problems due to decay that is slowed down but continues to progress through to late adult age instead.

For many people, this means repeated dental surgery visits, tooth drilling, filling and extractions, and the final outcome may still be complete tooth loss. During periods in between there can also be varying levels of pain, anxiety and financial loss, making life miserable.

Wider use of water fluoridation is thought to be a practical, low-cost public health measure that could offer lifetime benefit in combating this slower form of adult tooth decay. However, little evidence for or against this in adults has been published, which is why our study of anonymised NHS dental care patient data was proposed.

Areas with fluoridated water

The map below shows the small neighbourhood areas (LSOAs, covering around 1,500 people) that received fluoridated water between 2010 and 2020.

Areas that received water with a fluoride concentration of 0.7 mg fluoride / litre or above are highlighted. The local authority boundary lines are illustrated. Areas that are coloured white are those where we did not receive any sample information from the water companies.

Local authorities in which all of their neighbourhoods were fluoridated during this time were:

  • East Staffordshire;
  • Lichfield;
  • Cannock Chase;
  • Tamworth;
  • Birmingham; 
  • Sandwell;
  • Dudley;
  • Bromsgrove;
  • North Kesteven;
  • Newcastle upon Tyne;
  • Hartlepool

The water in Hartlepool has naturally higher levels of fluoride. This comes from the rocks that the water passes through.



Naturally Fuoridated

Not Fluoridated

Our aims

The main aim of the study is to find out whether or not 10 years of exposure to fluoridated water is associated with fewer invasive dental treatments (fillings, crowns, root canal treatment, extractions and so on) compared to no exposure to fluoridated water. We can take advantage of the patchy use of fluoridation in different regions to determine this.

The study will also examine possible dental health benefits, along with the costs of fluoridation. It will find out if fluoridation offers value for money.

It will also explore whether there is evidence of any reduction in oral health disadvantage from people’s socio-economic background, or where they live. As a result these factors could be addressed by policy makers, local authorities, and communities.

Public and patient engagement

The study has been designed with public and patients’ involvement and engagement (PPIE). These groups are represented on both the project Steering Committee and the Operational Management Group. Emily Lam is the PPI member of the LOTUS Operational Management Group.

Accessing our data

This is the first time that such detailed information on fluoride levels in England has been available.

We have made the data that we created on water fluoride concentrations publicly available. It can be used by other researchers under a creative commons license. This means that the data can be shared and adapted with appropriate attribution.

The dataset can be downloaded from The University of Manchester’s Open Data Repository, Figshare.

The information available includes:

  • LSOA 2011 code, LSOA 2011 name, year, and mean and median fluoride concentrations per year (in milligrams of fluoride per litre).
  • An indicator for whether an area was ‘fluoridated’ in each year, using a water fluoride concentration of 0.7 Mg F/L and above.

The image below shows a snapshot of the dataset that can be found in the Figshare open data repository.


Inputs and impacts

This study is very timely, coinciding with an increased focus on water fluoridation in government. The study will empower policy makers to make decisions on water fluoridation based on contemporary scientific evidence reviewed by dental professionals.

The power to make decisions about water fluoridation schemes in England currently rests with Local Authorities. In February 2021 the government produced a white paper which proposes to give the Secretary of State for Health and Social Care these powers. The government will also become responsible for the costs of setting up and running new water fluoridation schemes.

The Health and Care Bill 2021-2022 includes these proposals, with the aim of making the introduction of new water fluoridation programmes more straightforward. Following this, in September 2021 the four UK Chief Medical Officers made a joint statement.

Academic publications

  1. How effective and cost-effective is water fluoridation for adults? Protocol for a 10-year retrospective cohort study. [View paper]
    Moore, D. et al. BDJ Open 7, 2021.
  2. Water fluoride concentrations in England, 2009-2020. Nyakutsikwa et al. Community Dental Health 38, 2021. [View paper]
  3. Nyakutsikwa, B. et al. (2022) ‘Who are the 10%? characteristics of the populations and communities receiving fluoridated water in England.’, Community Dental Health, 39(4),247–253. [View paper]


Full report

The full and final report of the study results will be available when it has been approved by a peer review panel.

You will be able to view it online at the LOTUS NIHR Journals Library.

Influencing policy and public opinion

We want the results of our study to be used by politicians, decision-makers and the public.

To make sure our results are understandable, in addition to academic research papers, we will produce:

  • plain-language summaries of our results;
  • an infographic;
  • an animated video.

Watch this space for future updates.


This study is funded by the National Institute for Health Research (NIHR) Public Health Research: NIHR128533.

The views expressed are those of the author(s) and not necessarily those of the NIHR or the Department of Health and Social Care.

The study started on 1 February 2020 and is set to submit results to the funding committee, NIHR, on 31 July 2022. This includes a 6-month extension to the study due the impacts of the COVID-19 pandemic.

Useful documents

Contact us

Ms Deborah Moore, Research Associate


Dental Health Unit
Lloyd Street North
Manchester Science Park
M15 6SE
United Kingdom